1. Field of the Invention
This invention relates to devices and methods for sealing on multiple items used in a wellbore, e.g., drillpipe with umbilical and/or control lines.
2. Background Art
During drilling, completion, and production of an oil or gas well, multiple lines, such as a drill pipe, umbilical lines, and control lines, may be run in the well. There are occasions when the well needs to be sealed off or a section of the well needs to be isolated from other sections. For example, when a well penetrates a high pressure zone, the formation fluids and gas may rush into the wellbore. When this happens, the well is said to have taken a “kick.” The high pressure gas will quickly rise in the wellbore and expands its volume many times in the process. If this gas is allowed to reach the surface, it will blow out of the wellbore with enormous force, resulting in damages to the well equipment and injuries to the personnel. When a kick is detected, the well needs to be shut in right away, using a blowout preventer (“BOP”) so that the gas can be circulated out of the wellbore in a controlled manner. In order to successfully kill a kick, it is necessary that the well can be effectively sealed.
Conventionally, when sealing on multiple lines in a wellbore is required, an annular BOP is closed around these items. However, leakage often occurs at the interface (gaps) between the BOP and the various lines. The leakage could be dangerous because it creates a hazard to both workers and the environment. As noted above, wells are typically “shut in” to prevent a blowout after a gas “kick” is detected in the wellbore. The kick is controlled by sealing the annulus of the wellbore and “circulating out” the gas in a controlled process. If gaps exist between multiple items in the wellbore, the pressure integrity of the closed in well could be lost or reduced. In this case, the well control scheme is less effective and fluid that escapes the wellbore under pressure could produce a hazard to workers.
In addition, the leakage of wellbore fluids between multiple items can also lead to environmental contamination. Oilfield service and exploration companies take great precautions to prevent drilling fluid or “mud” from escaping the fluid circulation system at the rig site. Leakage of drilling mud can contaminate the ground around the BOP stack and, as previously mentioned, can contaminate the rig floor. This is a particular problem when oil-based or potentially corrosive muds are used in the drilling process.
Subsea operations present another difficulty. Environmental regulations prevent the uncontrolled release of drilling fluids into the surrounding subsea environment. The penalties for violating these measures are severe and costly cleanups may ensue. In addition, in offshore operations, the platform may move or twist with waves or winds, making it even more difficult to have a good seal on multiple lines in a riser or wellbore.
Elastomer sleeves have been used around items in the wellbore such as umbilical or control lines in an attempt to reduce the above problems. These sleeves were typically attached only to auxiliary lines. A drawback with such a method is that locating sleeves in the BOP, diverter, or similar oil field service product is difficult. The nature of BOP operation typically requires immediate action. Therefore, the sleeves would have to be aligned with the BOP at all times so that they would be in place for activation of the BOP.
U.S. Pat. No. 6,352,120 issued to Carbaugh discloses a multiple item sealing packing insert for use with oil filed service products in a wellbore. This patent is assigned to the assignee of the present invention and is incorporated by reference in its entirety. FIG. 1 shows a cross sectional view of a packing insert disclosed in this patent. As shown, the packing insert 11, which includes a top plate 50 attached to an elastomer body 52, is disposed within a diverter 13. As in a standard diverter, the diverter 13 has a housing cap 18, a piston 20, and a sleeve 22. The packing insert 111 is positioned in the diverter 13 by attaching its top plate 50 to the diverter housing cap 18 so that the packing insert 11 will always be available. Packing unit 24 in the diverter 13, when activated, radially compresses elastomer body 52 of packing insert 11. The elastomer body 52 in turn compresses the multiple items within the wellbore to form a tight seal.
While the above described approach can provide good seals on multiple items in a wellbore, there is still a need for further devices and methods that can provide good seals on multiple items in a wellbore.